1. Field of the Invention
The present invention relates to a laminator for manufacturing laminated objects such as photovoltaic cell modules, and more particularly, to a diaphragm mounting structure used in such a laminator.
2. Description of the Background Art
Examples of conventional laminators used to manufacture photovoltaic cell modules are described, for example, in Japanese Unexamined Patent Application Publication No. 9-141743 (JP-H09-141743-A), Japanese Unexamined Patent Application Publication No. 11-204811 (JP-H11-204811-A), and Japanese Registered Utility Model No. 3037201 (JP-3037201-U). For these types of laminators, an arrangement is employed in which upper and lower chambers are used. The upper chamber is movable vertically, or openably closable, with respect to the lower chamber, and has at its lower end a downwardly expandable diaphragm. The lower chamber has a support pedestal including a heating plate inside. When the upper chamber descends, or closes, it acts as a lid on the lower chamber.
The laminator is used in the following way: First, with the upper chamber raised and opened, a workpiece placed on a conveyer belt is conveyed to and placed on the heating plate provided in the lower chamber. A photovoltaic cell module workpiece has a bottommost layer that is a glass plate, on top of which are layered, in order, a sheet-like filler, the photovoltaic cell, and then another sheet-like filler, with an uppermost layer consisting of a sheet-like backing. The upper chamber is then stacked on top of the lower chamber and the air in both the upper chamber and the lower chamber is removed to form a vacuum, in which the workpiece is heated. Subsequently, air is introduced into only the upper chamber, causing the diaphragm to expand and sandwiching the photovoltaic cell module workpiece between the top face of the heating board and the diaphragm. The heat from the heating board melts the filler, causing a cross-linking reaction and curing to form the laminated object.
The usual method of fixing the diaphragm onto the upper chamber is to prepare a rectangular mounting frame shaped to fit the outer form of the upper chamber and sandwich and fix in place an outer peripheral portion of the diaphragm between the mounting frame and the upper chamber. Multiple bolt holes are opened in the periphery of the diaphragm, and multiple threaded screw holes are provided at corresponding positions in the mounting frame. Further, through-holes are provided at positions corresponding to the bolt holes and the threaded screw holes, such that, when the diaphragm is sandwiched between the upper chamber and the mounting frame, bolts are inserted in the through-holes, screwed into the threaded screw holes in the mounting frame, and tightened, fixing the diaphragm in place.
However, with such a mounting arrangement, when the diaphragm expands tensile stress is exerted on the portions of the periphery of the diaphragm that are compressed by the mounting frame. This tensile stress extends to the diaphragm bolt hole portions as well, the bolt holes tear, gradually grow large, and are damaged, and eventually become unable to maintain a vacuum. Moreover, if the diaphragm is damaged, it must, of course, be replaced. Removing a damaged diaphragm involves removing all the multiple bolts. These bolts must then be reinserted and re-tightened in order to mount the new diaphragm. Thus, replacing the diaphragm generates costs and adds to down-time of the laminator.
One approach to solving the above-described problem is a laminator like that shown in FIG. 6 and a diaphragm mounting structure, proposed by the applicant in Japanese Patent No. 3890206 (JP-3890206-B).
A laminator 10 shown in FIG. 6 includes a rectangular upper chamber 11 and a lower chamber 12 having a top face of the same shape as a bottom face of the upper chamber 11. The upper chamber 11 has a suction port 11a connected to a vacuum pump for depressurization, with a similar suction port 12a formed in the lower chamber 12. A support pedestal 13 on which is set a workpiece A consisting of a photovoltaic cell module is disposed inside the lower chamber 12. A diaphragm 14 is of the same shape as or slightly larger than the upper chamber 11, with a peripheral portion thereof sandwiched between the upper chamber 11 and a mounting frame 15.
The mounting frame 15 is a metal rectangular frame of the same shape and size as the upper chamber 11, on the outside of which are provided multiple hooks 15a. Clamps 16 are mounted on the upper chamber 11 at positions corresponding to the positions of the hooks 15a. Each of the clamps 16 includes a clamp lever 16a and a clamp ring 16b. The clamp lever 16a is rotatable about a shaft 16c. When the hook 15 is inserted into the clamp ring 16b and the clamp lever 16a is rotated from a substantially horizontal position to the vertical position shown in FIG. 6, the diaphragm can be compressed and sandwiched between the mounting frame 14 and the upper chamber 11.
A groove is formed in the bottom face of the upper chamber 11 that contacts the mounting frame 15. A first O-ring 17 is inserted into the groove to make contact between the upper chamber 11 and the diaphragm 14 airtight.
Similarly, a groove is formed in the bottom face of the mounting frame 15 and a second O-ring 18 inserted into the groove, such that, when the upper chamber 11 is set on top of the lower chamber 12, the space between the upper and lower chambers 11 and 12 is airtight.
With such a structure, there is no need to open bolt holes in the diaphragm 14, and thus the life of the diaphragm can be extended. In addition, using clamps instead of bolts in the mounting frame 15 simplifies the work of removing and replacing the diaphragm 14, enabling replacement time to be shortened.
However, in the arrangement disclosed in Japanese Patent No. 3890206 (JP-3890206-B), as noted, the mounting frame is metal and substantially the same size as the bottom face of the upper chamber 11. At the same time, the size of photovoltaic cells (and therefore of photovoltaic cell modules also) increases year by year. As a result, mounting frames are also getting larger and therefore also heavier, which means that they can be awkward to handle.